Sequential key locking and releasing arrangement

ABSTRACT

A taximeter is to be set to different operational conditions by corresponding keys. It is required that a certain starting condition, namely the condition &#39;&#39;&#39;&#39;vacant&#39;&#39;&#39;&#39; is first obtained by operation of a &#39;&#39;&#39;&#39;vacant&#39;&#39;&#39;&#39; key, before any other condition is selected, which is accomplished by locking all keys in a normal inoperative position, except the &#39;&#39;&#39;&#39;vacant&#39;&#39;&#39;&#39; key which, when actuated, unlocks all other keys for subsequent operation.

[451 July 11, 1972 United States Patent Schuh References Cited UNITEDSTATES PATENTS [$4] SEQUENTIAL KEY LOCKING AND RELEASING ARRANGEMENT2,973,664 3/l96l Williams.........t..................74I483PB [72]Inventor: Eduard Schuh, Villingen, Germany [73] Assignee: KlenzleApparate Gmbl-l, Villingen,

Primal Examiner-Milton Kaufman AnomeyMichael S. Striker Schwanwald,Germany April 27, 197] 221 Filed:

ABSTRACT A taximeter is to be set to difierent operational conditionscorresponding keys. It is required that a certain starti tion, namelythe condition 21 Appl. No.: 137,860

y ng condivacant" is first obtained by opera- 20 007's tion of a vacant"key, before any other condition is selected,

which is accomplished by locking all keys in a normal inopera- -74/483200/ 5 E tive position, except the "vacant" key which, when actuated. lunlocks all other keys for subsequent operation. .74/483 PB; 200/5 E[30] Foreign Application Priority Data April 29, 1970 [$2] U.S. Cl.

[51] Int. Cl.

IDChhmJDnwlngFlgures PATENTEUJuL 11 m2 3. 6 75. 504

sum 1 OF 2 W n/r0? spun; S60 0 If PATENTEUJUL 1 1 m2 SHEET 2 nr w M 9 Me 8 SEQUENTIAL KEY LOCKING AND RELEASING ARRANGEMENT BACKGROUND OF THEINVENTION It is known to set taximeters to different operationalconditions and functions such as vacant," rate I," "rate 2," cash," andso forth by turning of a flag or a knob mounted on the taximeter casing.The angular displacements of the flag or knob are transmitted to acontrol shaft provided with cam lugs by which the respective differentconditions of the taximeter are obtained in accordance with the angularpositions of the flag or knob.

It is also known to substitute for the knob or flag, an electric motorby which the control cam shaft is stepwise displaced, as disclosed inthe German Pat. Nos. 1,083,581 and 1,092,709. A control key is providedby which the electromotor is actu ated to turn the control cam shaft tothe respective next following position, for example from the positionvacant" to the position rate I," from the position "rate I" to theposition rate 2, and so forth.

It is necessary to arrest the control cam shaft in each angular positioncorresponding to a particular operational condition of the taximeter.Since it is necessary to arrest the control cam shaft in this manner,the control by means of a flag or knob, and also by means of anelectromotor, is difficult, particularly if the taximeter is to operateat four different rates, and should permit direct movement from thevacant" condition to the rate 3" condition, and later from the "cascondition again to the vacant" condition. For example, if the controlcam shaft is to be turned from the vacant" position to the positioncorresponding to rate 3, it is necessary to operate the control switchthree times, and when the taximeter and control cam shaft is to beshifted from the position representing "rate 3 to the position cash, thecontrol switch has to be two times operated before the motor turns thecontrol cam shaft to the correct position for operating the taximeter inthe corresponding condition.

When a flag or knob is used, certain positions of the control cam shafthave to be skipped, and visual control is necessary for determinationwhether the flag or knob is in the correct position, which isundesirable for modern taxi operation. Furthermore, electronictaximeters have been recently constructed in which the severaloperational conditions are not obtained by angular stepwise displacementof the control cam shaft, but by operating a key or pushbuttoncontrolling a set of switches for each operational condition of thetaximeter.

For taxicab operations, it is absolutely necessary that the taximeter iscleared before a new trip is started, that means that the previouslyindicated fare must disappear from the indicator, and an amount of moneyindicated when a new customer has entered the taxi. This new amount ofmoney represents an initial fare which has to be paid, irrespective ofthe further use of the taxicab.

Therefore, it is necessary that after termination of each trip, thetaximeter should only be operated after it has been, at leastmomentarily, placed in the condition vacant. In other words, a certainsequence of operation, which is obtained without difficulties by turninga knob or flag, must be assured even if selector keys associated withthe different positions of the taximeter are used, which would beoperable in any sequence, including an undesired sequence in which thetaximeter is not temporarily set to the "vacant" condition between theuses of the taxicab by two different customers.

SUMMARY OF THE INVENTION It is one object of the invention to provide akey locking and releasing arrangement, particularly suited for ataximeter, which permits actuation of the keys only in a predeterminedsequence.

Another object of the invention is to provide a key locking andreleasing arrangement for a taximeter in which the keys correlated withdifferent operational conditions of the taximeter, must be operated in asequence starting with the operation of the "vacant" key.

Another object of the invention is to operate a taximeter correctly bymeans of a series of keys so that no flag or knob is required.

With these objects in view, the present invention provides a keyboardfor the operation of a taximeter, or like apparatus, in which a key iscorrelated with each operational condition of the taximeter. In order toobtain the proper sequence of key operations, locking means are providedfor locking all keys, except the key associated with the vacant"condition which can be actuated to operate the locking means to releaseall other keys for selection of a desired condition of the taximeterafter the same was in the "vacant condition.

The arrangement of the invention makes it possible that any one ofselector keys correlated with taximeter conditions rate I," rate 2, etc.or cash," can be operated in any desired sequence, while before a newtrip is started, the "vacant" key must be operated.

The principle of the invention is applicable to other apparatus having aplurality of different operational conditions, and requiring a startingcondition, obtained by a starting key, before any other selector key isoperated to obtain another operational condition of the apparatus.

A sequential key means locking and releasing arrangement according toone embodiment of the invention comprises a set of selector keyscorrelated with different conditions of an apparatus, such as ataxirneter, and being movable between normal inoperative positions, andactuated positions for placing the apparatus in the respectiveconditions; releasable locking means for locking the selector key in thenormal inoperative positions; and a starting key movable between aninoperative normal position, and an actuated position for obtaining therequired starting condition of the apparatus, such as the "vacantcondition of a taximeter.

The starting key in the actuated position operates the locking means torelease the selector keys so that any condition of the apparatus can beselected by operation of the respective selector key only after theapparatus has been set to the required starting condition by thestarting key, which is the "vacant" key in a taximeter.

The locking means preferably includes a shiflable locking slide which isbiassed by springs and has abutrnents and slots for projections on thestems of the selector keys, while a projection on the stern of thestarting key engages a slanted face of the locking slide for moving thesame to a position unlocking the selector keys when the starting key ismoved to the actuated position.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a perspective viewillustrating a taximeter provided with a set of keys in accordance withthe invention;

FIG. 2 is a fragmentary perspective view, partly exploded, illustratingan embodiment of the invention; and

FIG. 3 is an elevation illustrating the cooperation of the keys with thelocking slide of the embodiment of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, in ahousing I having a front plate 2, a cover sheet 3 with indicia isarranged which has windows 4 through which indicator means showing thefare can be observed. Another window 5 permits a view of other indicatormeans showing additional charges, and windows 6 permits the reading ofthe indication of totalizers. Casing 1 has a rectangular opening inwhich a control unit 8, including a set of key buttons 10 of keys 34 to39 is mounted. Key buttons 10 are hollow and transparent, and areilluminated to show indicia so that it is apparent that key 38 iscorrelated with the operational condition vacant," key 37 is correlatedwith the operational condition "rate 1," and key 39 is correlated withthe operational condition cash." If the taximeter can be set to fourdifferent rates, in which the same mileage is differently charged, inaddition to the keys 37, 38, 39, further three keys 34, 35, 36 for theadditional rates "rate 2," "rate 3," and rate 4, are provided.

As shown in FIG. 2 and 3, each key includes a hollow prismatictransparent key button 10, which is mounted on the respective key stem11 for angular movement between a normal position, and a servicingposition shown for key 39 in FIG. 2. Each key stem 11 has two bent lugs12 supporting a pin 13 which is secured to the respective pushbutton 10.A spring, not shown, holds the key buttons in the closed position inwhich keys 34 to 38 are shown, but each key button 10 can be opened foraccess to a lamp 15 so that the same can be exchanged, when required, ina convenient manner. Since the transparent key buttons 10 have printedindicia, representing the operational conditions of the taximeter,servicing of the lamps 15 while the respective key buttons 10 remainconnected with the apparatus, prevents a mix-up between the several keybuttons.

The stems of all keys 34 to 39 are guided in an angular support platewhich has two walls 16 and 17. A connector plate 18 is mounted on theangular wall 16, 17 and has connecting elements for connecting the lamps15 to a source of voltage. The shape of the stems 11 is best seen inFIG. 3. Each stem 11 has a projecting portion 19 which projects towardthe wall 17. The lower portion of the exploded view of FIG. 2, isseparated from the upper portion by a section directly under the stems11 and through the projecting portions 19. Each key stem 11 has a cutout20, and an arresting projection 21 adjacent cutout 20. The rear end ofeach stem 11 has a slot 22 through which a pin 23 secured to wall 17passes. Torsion springs 24, wound about pin 23, and engaging stems I]urge the stems 11 and the respective keys 34 to 39 to the normalinoperative position. The rear ends 25 of each stem 11 is slanted andcooperates with a set of contacts 26, so that operation of any key 34 to39 selects an operation of the taximeter, corresponding to theoperational condition, such as operation at a certain rate. Actuation ofthe set of contacts 26 associated with the key 38, will place thetaximeter in a starting condition, set to the condition "vacant, whilethe selector keys 34 to 37 and 39 select other operational conditionswhich have to follow the vacant" condition. The number and arrangementof the contacts of each set 26 depend on the construction of thetaximeter, and each set 26 may include normally closed, normally opened,and shifting contacts. The specific manner in which the taximetercircuit is influenced by operation of any of the sets of contacts 26, isnot an object of the invention.

Locking means are provided for locking all selector keys 34 to 37 in thenormal inoperative position, while the starting key 38, associated withthe "vacant" condition is not locked. A locking slide 30 is mounted inbent over wall portions 14 and 29 of supporting plate 17, as best seenin the lower portion of FIG. 2, and is slidable in the same inlongitudinal direction between a normal position in which abutments 48,see FIG. 3, are located in the path of movement of the projections 19 ofkeys 34 to 37 and block movement of the same in the normal position oflocking slide 30 into which the same is urged by a spring 30' secured toa hook portion of the fixed support plate 17. The projecting portion 19of key 38 cooperates with the slanted face 33 of a recess 32 so that thedepression of key 38 will cause engagement between projection 19 andslanted face 33 for moving locking slide 30 to the right as viewed inFIG. 3 to a releasing position in which the recesses 31 are located inthe path of movement of the projections 19 of keys 34 to 37, permittingmovement of any selected key to an actuated position. During movement ofany key to the actuated position, the respective pin 23 slides in therespective slot 22 while spring 24 is tensioned. In the position of thelocking slide 30 shown in FIG. 3, selector keys 34 to 37 are locked, butstarting key 38 is operable. Key 39, associated with the "cash conditionof the taximeter, is not locked since a special construction is shown inFIG. 3. However, it is possible to extend locking slide 30 so thatselector key 39 is also locked in the normal position in which it isshown in FIG. 3. When key 38 is operated and has pushed locking slide 30to the releasing position described above, key 38 is arrested by anarresting means 40 so that the stem 11 of key 38 remains in the positionshown in the upper portion of FIG. 2, while the projections 19 of theselector keys are located opposite recesses 31, permitting movement ofany selector keys 34 to 37 to the actuated position.

Any actuated key is arrested in the actuated position by an arrestingcomb 40 which has a set of prongs 44 respectively cooperating witharresting projections 21 on the stems ll of the keys. Arresting comb 40is mounted for angular movement and is biassed by springs 41 and 42 toturn in clockwise direction, as viewed in FIG. 2 to a position in whichthe prongs 44 respectively rest on the stems 11.

When one of the keys is depressed, and the respective stem 11 isdisplaced, the bent-over portion of the respective stem 11 displacesarresting comb in counter-clockwise direction since a prong 44cooperates with the bent-over portion of the respective stem 11. Whenthe arresting projection 21 has passed the prong 44, arresting comb 40is returned by springs 41 and 42 to its initial position, and engagesarresting projection 21 to arrest the respective stem and key in theactuated position, as shown for key 38 and the respective stem 11 in theupper portion of FIG. 2.

When after operation of key 38, key 37 is depressed, for example, thebent-over portion of stem 11 of key 37 lifts the arresting comb 40 againso that first the stem 11 and arresting projection 21 of key 38 isreleased by the arresting prong 44 so that key 38 can return to itsnormal position due to the action of its spring 24. The depressed key 37first lifts the arresting comb, and is then arrested by engagement ofthe respective prong 44 with arresting projection 21 thereof.

All prongs 44 of arresting comb 40 are constructed in the same manner,except a prong 43 which cooperates with key 39 which is correlated withthe operational condition cash" of the taximeter. Depression of key 39causes an angular displacement of arresting comb 40 in counter-clockwisedirection, and consequently release of all other keys. Due to the shapeof prong 43, key 39 is not arrested but returns to its normalinoperative position due to the action of spring 24. The reason for thisconstruction will be explained hereinafter, and is due to a particularcircuit and construction of the taximeter.

In order to prevent that several keys are depressed at the same time, aplurality of round circular discs 28 is located in a confined spacebetween walls 14 and 29, and wall 17 and locking slide 30. The sum ofall diameters of the round discs 28 is less than the distance betweenthe walls 14 and 29, and corresponds to the width of projections 19which normally guide the key stems in slots of plates 16 and 19 in whichcorresponding matching slots 45 are provided. When any key is operated,the respective projection 19 enters between two round discs 28, pushingthe discs apart so that the free space is taken up, and no other keystem can enter between the round discs 28 whereby each key in theactuated position, locks all other keys in the normal inoperativeposition.

As noted above, in the "vacant" condition of the taximeter, thepreviously indicated fare must be cleared, and all electrical andmechanical parts returned to the initial condition. At the same time,the operation of the vacant key will result in the indication of aninitial fare which must be paid by the customer even if he uses thetaxicab only for a very short distance. Four different rates or tariffsare associated with the selector keys 34 to 37. Operation of these keyssets the taximeter to the respective rate, so that different fares willbe charged for the same distance. The time rate is also operative, whichmeans that the fare is increased even if the car does not travel, butwaits for the customer, or stops in traffic.

However, when the special key 39 cash" is operated, the time drive isdisconnected, and only the distance drive remains operative forindicating the fare for travelled distances, while no additional fare isindicated when the taxicab does not move.

The purpose of the cash key 39 is to pennit the driver of the taxicab,to move on for a short distance after completion of a trip afterstopping the car for the purpose of unloading bags and suitcases. Duringsuch unloading operations, it may be necessary to move the car a smalldistance, which is to be charged, but no charge is to be made to thecustomer for the time required for unloading the vehicle after thedestination has been reached. Since in the cash condition of thetaximeter, the time drive is disconnected, the time during which thetaxicab is at a standstill during unloading operations, is not charged.

Before a new trip is started, selector keys 34, 35, 36, 37 are locked,because projections l9 are located opposite the pro jecting abutments 48of locking slide 30. The driver can operate the cash" key 39, since noabutment 48 is located in the path of movement of projection 19 of key39, and when key 39 is in the actuated position, it is not arrested byarresting comb 40 due to the special construction of the respectiveprong, and is returned by spring 24 to its normal inoperative positionso that the taximeter is not set to the condition cash. if the drivercorrectly operates the vacant key first, which must be operated when anew trip is started, locking slide 30 is displaced due to the engagementof projection 19 with the slanted face 33, and key 38 operates thearresting comb 40, as described above, so that the first prong 44engages behind the arresting projection 21 of stem 11 of key 38, asshown in FIG. 2.

The taximeter now properly indicates the initial fare, and previousindications are cleared.

When one of the selector keys 34 to 37 is actuated, the taximeter is setto the respective selected rate or tariff. The respective selector keyis arrested by a prong 44 of arresting comb 40, while at the same time,the lifted arresting comb 40 releases the arresting projection 21 of thestem 11 of key 38, so that the key 38 returns to its normal inoperativeposition due to the action of the respective spring 24.

Operation of any key 34 to 37 is possible after operation of key 38because the same shifts locking slide 30 to the releasing position inwhich the projections 19 are located opposite the recesses 31. Any ofthe selector keys 34 to 37 can be actuated in any desired sequence sothat at any time a different rate may be selected. Each operatedselected key releases the last operated and arrested key, and isarrested in the advanced actuated position. Return of any actuated keyto its normal position is required before the locking elements 28 permitany other key to move to the actuated position. Each selector key in theadvanced actuated position, holds the locking slide 30 in the releasingposition due to the engagement between its projection 19 with theshoulder of the respective abutment 48 when projection 19 is located inrecess 31.

At the end of a trip, the driver depresses "cash key 39, so that therespective key in the actuated position is released to return to itsnormal position under the action of spring 24, and since its projection19 releases the shoulder of abutment 48, spring 34 returns locking slide30 to the normal locking position shown in FIG. 3.

All the selector keys 34 to 37 are again locked by the locking slide, sothat the driver must actuate the vacant" key 38 before he operates oneof the selector keys 34 to 37. Consequently, the driver is compelled tooperate the vacant key 38 after he has operated the cash" key 39 so thatthe taximeter starts a new trip in the correct condition in which theindication of the previous fare is cleared, and a new initial fare isindicated. Due to the sequential locking and releasing arrangement ofthe invention, keys can be used instead of a tumable knob or flag forinitiating and continuing operations of the taxicab in a necessarysequence. The interlock arrangement of the invention accomplisheslocking functions which are conventionally obtained by a tumable flag orknob due to the fact that the same must always return to the startingposition corresponding to the condition vacant of the taximeter.Generally speaking, key 38 is a starting key obtaining a startingcondition of the taximeter which must precede setting of the taximeterto any other operational condition.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofkey locking and releasing arrangements in other types of key locking andreleasing arrangements differing from the types described above.

While the invention has been illustrated and described as embodied in asequential key locking and releasing arrangement for the keys of ataximeter, it is not intended to be limited to the details shown, sincevarious modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

I claim:

1. Sequential key locking and releasing arrangement for an apparatushaving different operational conditions, comprising: a set of selectorkeys correlated with the different conditions of the apparatus,respectively, and being movable between normal inoperative positions,and actuated positions for placing the apparatus in said conditions,respectively; releasable locking means for locking said selector keys insaid normal inoperative positions; and a starting key movable between aninoperative normal position, and an actuated position for obtaining arequired starting condition of the apparatus, said starting key in saidactuated position operating said locking means to release said selectorkeys of said set so that any condition of the apparatus can be selectedby operation of the respective selector key only after the apparatus hasbeen set to the required starting condition by said starting key.

2. Arrangement as claimed in claim I wherein said apparatus is ataximeter; wherein said starting key is correlated with the vacantcondition of the taximeter, and is a vacant" key.

3. Arrangement as claimed in claim 1 wherein each selector key and saidstarting key includes a key stem; wherein said locking means includes alocking slide extending across said key stems, and spring means urgingsaid locking slide to a normal position locking said key stems of saidselector keys, said locking slide being operable by said key stem ofsaid starting key in said actuated position to move to said releasingposition for unlocking said key stems of said selector keys.

4. Arrangement as claimed in claim 3 wherein said locking slide has aslot and an abutment for each key stem of said selector keys so thatsaid abutments block said selector keys in said normal position of saidlocking slide, and said slots permit movement of said selector keys tosaid actuated positions in said releasing position of said lockingslide, said locking slide having a slanted face cooperating with saidkey stem of said starting key so that movement of said starting key tosaid actuated position moves said locking slide to said releasingposition.

5. Arrangement as claimed in claim 1 comprising arresting means forarresting said selector keys and said starting key in said actuatedpositions, respectively; and wherein movement of any selector key tosaid actuated position operates said arresting means to release saidstarting key arrested in said actuated position; and wherein subsequentmovement of any other selector key operates said arresting means torelease the preceding last arrested selector key.

mm NRA 6. Arrangement as claimed in claim wherein each selector key andsaid starting key includes a key stern having a projection; wherein saidarresting means includes a spring biassed arresting comb mounted forangular movement and having prongs respectively abutting said key stemsso that during movement of any key to said actuated position saidprojection lifts said arresting comb whereupon said projection isengaged by the respective prong for arresting the respective key in saidactuated position, and so that movement of any other key to saidactuated position lifts said arresting comb to release said projectionof the last operated key whereupon said other key is arrested.

7. Arrangement as claimed in claim 6 further comprising a special keyhaving a special key stem with a smooth surface cooperating with a prongof said arresting comb for lifting said arresting comb to release saidprojection of the last operated and arrested key during movement of saidspecial key to said actuated position, said smooth surface slidinglyengaging the respective prong so that said special key is not arrestedin said actuated position thereof.

8. Arrangement as claimed in claim 7 wherein said apparatus is ataximeter; wherein said starting key is correlated with the vacantcondition of said taximeter; wherein said start ing key is a vacant key;and wherein said special key is a cash key correlated with a conditionof said taximeter in I which only the distance of travel is measuredtransparent hollow push button mounted on said key stern for angularmovement between a normal position for enveloping a lamp, and aservicing position in which the lamp is accessible.

l0. Arrangement as claimed in claim I wherein said selector keys andsaid starting key are spring-biassed toward said normal position;wherein each selector key and said starting key includes a key stemhaving a projection; wherein said locking means includes a locking slideextending across said key stems and having a slot and an abutment foreach projection of said selector keys, and spring means urging saidlocking slide to a normal position in which said abutments are locatedin the paths of movement of said projections of said selector keys, saidlocking slide having a slanted face cooperating with said projection onsaid key stern of said starting key so that movement of said startingkey to said actuated position moves said locking slide to a releasingposition in which said slots are located in the paths of movement ofsaid projections of said selector keys; comprising a supporting plateparallel with said locking slide and forming a confined space with thesame, and a row of round locking elements located in said space so thatsaid projection of any single key stem enters between two lockingelements during movement of the respective key to said actuated positionwhereby said locking elements block movement of said projection of anyother key stern during movement of the respective other key to saidactuated position.

* k t t i

1. Sequential key locking and releasing arrangement for an apparatushaving different operational conditions, comprising: a set of selectorkeys correlated with the different conditions of the apparatus,respectively, and being movable between normal inoperative positions,and actuated positions for placing the apparatus in said conditions,respectively; releasable locking means for locking said selector keys insaid normal inoperative positions; and a starting key movable between aninoperative normal position, and an actuated position for obtaining arequired starting condition of the apparatus, said starting key in saidactuated position operating said locking means to release said selectorkeys of said set so that any condition of the apparatus can be selectedby operation of the respective selector key only after the apparatus hasbeen set to the required starting condition by said starting key. 2.Arrangement as claimed in claim 1 wherein said apparatus is a taximeter;wherein said starting key is correlated with the vacant condition of thetaximeter, and is a ''''vacant'''' key.
 3. Arrangement as claimed inclaim 1 wherein each selector key and said starting key includes a keystem; wherein said locking means includes a locking slide extendingacross said key stems, and spring means urging said locking slide to anormal position locking said key stems of said selector keys, saidlocking slide being operable by said key stem of said starting key insaid actuated position to move to said releasing position for unlockingsaid key stems of said selector keys.
 4. Arrangement as claimed in claim3 wherein said locking slide has a slot and an abutment for each keystem of said selector keys so that said abutments block said selectorkeys in said normal position of said locking slide, and said slotspermit movement of said selector keys to said actuated positions in saidreleasing position of said locking slide, said locking slide having aslanted face cooperating with said key stem of said starting key so thatmovement of said starting key to said actuated position moves saidlocking slide to said releasing position.
 5. Arrangement as claimed inclaim 1 comprising arresting means for arresting said selector keys andsaid starting key in said actuated positions, respectively; and whereinmovement of any selector key to said actuated position operates saidarresting means to release said starting key arrested in said actuatedposition; and wherein subsequent movement of any other selector keyoperates said arresting means to release the preceding last arrestedselector key.
 6. Arrangement as claimed in claim 5 wherein each selectorkey and said starting key includes a key stem having a projection;wherein said arresting means includes a spring biassed arresting combmounted for angular movement and having prongs respectively abuttingsaid key stems so that during movement of any key to said actuatedposition said projection lifts said arresting comb whereupon saidprojection is engaged by the respective prong for arresting therespective key in said actuated position, and so that movement of anyother key to said actuated position lifts said arresting comb to releasesaid projection of the last operated key whereupon said other key isarrested.
 7. Arrangement as claimed in claim 6 further comprising aspecial key having a special key stem with a smooth surface cooperatingwith a prong of said arresting comb for lifting said arresting comb torelease said projection of the last operated and arrested key duringmovement of said special key to said actuated position, said smoothsurface slidingly engaging the respective prong so that said special keyis not arrested in said actuated position thereof.
 8. Arrangement asclaimed in claim 7 wherein said apparatus is a taximeter; wherein saidstarting key is correlated with the vacant condition of said taximeter;wherein said starting key is a ''''vacant'''' key; and wherein saidspecial key is a ''''cash'''' key correlated with a condition of saidtaximeter in which only the distance of travel is measured. 9.Arrangement as claimed in claim 1 wherein each of said selector keys andsaid starting key include a key stem, and a transparent hollow pushbutton mounted on said key stem for angular movement between a normalposition for enveloping a lamp, and a servicing position in which thelamp is accessible.
 10. Arrangement as claimed in claim 1 wherein saidselector keys and said starting key are spring-biassed toward saidnormal position; wherein each selector key and said starting keyincludes a key stem having a projection; wherein said locking meansincludes a locking slide extending across said key stems and having aslot and an abutment for each projection of said selector keys, andspring means urging said locking slide to a normal position in whichsaid abutments are located in the paths of movement of said projectionsof said selector keys, said locking slide having a slanted facecooperating with said projection on said key stem of said starting keyso that movement of said starting key to said actuated position movessaid locking slide to a releasing position in which said slots arelocated in the paths of movement of said projections of said selectorkeys; comprising a supporting plate parallel with said locking slide andforming a confined space with the same, and a row of round lockingelements located in said space so that said projection of any single keystem enters between two locking elements during movement of therespective key to said actuated position whereby said locking elementsblock movement of said projection of any other key stem during movementof the respective other key to said actuated position.